Elizabeth Warren, who has been the nation’s leading congressional fund-raiser this year, today announced raising $12.12 million during the most recent quarter for her bid to unseat Senator Scott Brown, who raised $7.45 million.

The period from July 1 through Sept. 30 was the most lucrative three-month for the Democrat since entered the Senate race last year. Warren’s previous best was the prior quarter, running from April through June, when she raised $8.6 million. Brown, the Republican incumbent, also had his best quarter, topping the $4.97 million he raised from April through June.

The senator said his haul allowed him to enter the campaign’s homestretch with $10.2 million cash on hand.

Warren has less cash on hand than Brown, about $7.3 million, according to her aides. They said that is, in part, because Warren spent just over $3 million to pay for advertisements that will run during the last three weeks of the election. Pre-paying allows a candidate to lock in lower ad rates.

Reports from the Senate candidates were due to be filed with Federal Election Commission today.

Overall, Warren, a Harvard Law School professor and consumer advocate, has raised about $36.3 million for her first bid for elective office. Brown has raised about $27.45 million so far, but was also helped by $7 million left over from his January 2010 special election.

“Tens of thousands of people across Massachusetts have joined this campaign because they know that Elizabeth will fight for them in the US Senate,” said a statement from Michael Pratt, Warren’s campaign finance director. “While Scott Brown has stood with billionaires, Big Oil, and Wall Street – and supports Republican control of the Senate – Elizabeth Warren has been there for middle-class families and small businesses. This strong support will help propel the campaign to victory in November.”

Brown’s campaign said it will also have ample money to stay on the air.

“As we head into the final weeks of the campaign, Scott Brown’s message of being an independent fighter for Massachusetts jobs is clearly resonating with voters,” said a statement from John Cook, finance director for the Brown campaign. “We are truly humbled by the outpouring of support that has led to our best fund-raising quarter to date. Our campaign will have the resources it needs to starkly lay out the difference between Scott Brown’s proven record of pushing pro-jobs legislation versus Elizabeth Warren’s job-destroying policies of higher taxes that would crush our fragile economy.”

Warren has steadily closed a cash advantage that Brown held at the outset of their race. Though Brown has not raised as much as Warren throughout the current campaign, he began it with the leftover $7 million.

He has also proven to be among the nation’s leading congressional fund-raisers.

The Globe’s Beth Healey, who analyzed previous federal filings, reported today that Brown’s largest financial supporters are a who’s who of finance and business, while Warren has drawn support primarily from universities, law firms, and left-leaning political groups

The prodigious sums of money have allowed both candidates to run continuous television advertisements that are expected to continue until Election Day on Nov. 6.